/Engine/Source/Runtime/Engine/Classes/Animation/AttributesContainer.h
Adds, if not yet existing, a new attribute type/value entry for the specified InScriptType.
The ptr to the added/existing entry, to be used for populating the data, nullptr if adding it failed
uint8 * FindOrAdd ( const [UScriptStruct](API\Runtime\CoreUObject\UObject\UScriptStruct) * InScriptStruct, const [FAttributeId](API\Runtime\Engine\Animation\FAttributeId) & InAttributeId )